An inhibitor is a chemical agent added to a fluid system to inhibit or prevent an undesirable reaction from occurring within the fluid or with the materials present in the surrounding environment. Numerous inhibitors are used in the petroleum, petrochemical, and chemical industries. For example, corrosion is recognized as a serious problem in the development of geoenergy sources, including oil and natural gas reserves, geothermal, and geopressured systems and leads to great costs to the industry every year. Corrosion problems are greatly aggravated by the presence of acid gases such as hydrogen sulfide and carbon dioxide, and by the co-production of brine solutions. As an alternative to the use of high alloy components which are expensive in relation to common carbon steels, a range of corrosion inhibitors have been researched for mitigating the occurrence of corrosion in the production and servicing of oil and gas wells. The use of inhibitors may permit the use of regular carbon steel components rather than more expensive alloys. Corrosion inhibitors are injected into process streams (for example in acidizing treatments) to inhibit corrosion of metal equipment and wellbore components and are generally carried in liquid steams to contact inner surfaces and other contact surfaces of plant equipment. A corrosion inhibitor may create a protective film or passivation layer on a metal surface and thus inhibit corrosion by acidic components in a process stream. For example, drill pipe may be coated with amine film to arrest corrosion of the pipe on contact with air.
Corrosion problems may be greater when production from deeper formations is pursued. Production of deep, sour gas reserves and deep geopressured zones may involve high bottom hole temperatures (as high as 200° C.) and pressures (up to 140 MPa). Additionally, the produced gas may contain primarily acid gases such as carbon dioxide and hydrogen sulfide and minor amounts (as low as about 20%) of desired hydrocarbon such as methane. The acid gases may be present along with high salinity sodium chloride brine in the producing formations, with chloride contents ranging as high as several moles per kilogram of water. Lower pH fluids are generally more corrosive, and, with pH values which may be as low as 2 to 3, deep downhole fluids may be very corrosive.
In the case of geopressured and geothermal systems, the acid gas content is typically much lower. However, these systems may be characterized by high salinity brines (as much as 150,000 ppm of chloride, for example) and high bottom hole temperatures (up to 310° C.). These fluids may have higher pH values than those estimated for deep sour gas systems, generally in the range of 4 to 5, however higher bottom hole temperatures may increase the potential for corrosion in such systems.
Conditions such as high acid gas (e.g., hydrogen sulfide) concentration, severe scale deposition, ice or hydrate formation, and flow reduction may be inhibited by injection of inhibitors. A challenge to the application of inhibitors is that inhibitors are typically used in small amounts as low as parts per million and care must be taken to adequately introduce the small quantity such that the inhibitor is uniformly dispersed in the fluid to be treated.
Accordingly, there is a need in industry for improved systems and processes for injecting inhibitors into fluids whereby increased process fluid throughput, increased degree of inhibition of undesirable component or condition, and/or the use of reduced amounts of generally costly inhibitor may be achieved.